startop: Add timestamps for IntentStarted and ActivityLaunchFinished.

The timestamps are used to compute duration of TotalTime and ReportFullyDrawn.

TotalTime = t(ActivityLaunchFinished) - t(IntentStarted)
ReportFullyDrawn = t(ReportFullyDrawn) - t(IntentStarted)

where t(x) is the timestamp of x.

Bug: 137786390
Bug: 137784595
Test: Make
Test: atest CtsWindowManagerDeviceTestCases:ActivityMetricsLoggerTests
Change-Id: I75c0be8508499dce186fd392e79b67b2fefc8842
diff --git a/services/core/java/com/android/server/wm/ActivityTaskManagerService.java b/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
index 750fc68..423e010 100644
--- a/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
+++ b/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
@@ -6026,10 +6026,10 @@
 
         @Override
         public void notifyAppTransitionStarting(SparseIntArray reasons,
-                long timestamp) {
+                long timestampNs) {
             synchronized (mGlobalLock) {
                 mStackSupervisor.getActivityMetricsLogger().notifyTransitionStarting(
-                        reasons, timestamp);
+                        reasons, timestampNs);
             }
         }